Projection lens and projection display apparatus using the same

ABSTRACT

A projection lens includes a plurality of lens units, and a diaphragm, wherein in a case where a lens unit that moves in an optical axis direction of the projection lens during focusing serves as a focus lens unit among the plurality of lens units, at least one lens included in a lens unit that is different from the focus lens unit among the plurality of lens units and is disposed more towards a reduction conjugate side than the diaphragm is configured to move in the optical axis direction when an amount of field curvature is adjusted to focus on a curved projection surface, and wherein when the amount of field curvature is adjusted, both the at least one lens and the focus lens unit move in the optical axis direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/258,147 filed Jan. 25, 2019, which claims the benefit of JapanesePatent Applications No. 2018-013036, filed Jan. 29, 2018, and No.2018-101007, filed May 25, 2018, all of which are hereby incorporated byreference herein in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a projection lens system and aprojection display apparatus using the projection lens system.

Description of the Related Art

In recent years, there has been a demand for a projector capable ofprojecting an image without blur not only on a flat screen but also on acurved screen. In order to project an image with less blur on a flatscreen and a curved screen, a projection lens needs to have a functionfor adjusting an amount of field curvature.

As a projection lens in which an amount of field curvature isadjustable, a projection lens discussed in Japanese Patent ApplicationLaid-Open No. 2015-49340 is known. To correct the field curvature of theprojection lens caused by temperature variation, the projection lensdiscussed in Japanese Patent Application Laid-Open No. 2015-49340 isconfigured to move a part of the lenses (correction lens) in the lensunit disposed on the liquid crystal panel side in the optical axisdirection of the projection lens. While an amount of filed curvature isadjustable in the projection lens discussed in Japanese PatentApplication Laid-Open No. 2015-49340, such a configuration is not forthe purpose of projecting an image with less blur on the above-describedcurved screen.

The field curvature which occurs when the above-described correctionlens moves is enlarged by a lens that is a lens among lenses disposedmore towards the anterior side (enlargement conjugate side) than thecorrection lens and has a magnifying effect. Thus, if many lenses havinga magnifying effect are disposed more towards the anterior side than thecorrection lens, the amount of movement of the correction lens forachieving a certain amount of field curvature decreases. This allowsdownsizing of the entire projection lens.

However, in the projection lens discussed in Japanese Patent ApplicationLaid-Open No. 2015-49340, the correction lens is positioned more towardsthe anterior side than a diaphragm, i.e., near the center of the entireprojection lens. Therefore, in comparison with a case where thecorrection lens is positioned more towards the posterior side (reductionconjugate side) than the diaphragm, there is a small number of lensesthat have a diffusion effect and are disposed more towards the anteriorside than the correction lens. This increases the amount of movement ofthe correction lens.

More specifically, when a user tries to project an image with less bluron a curved screen using the projection lens discussed in JapanesePatent Application Laid-Open No. 2015-49340, it is necessary to increasethe amount of movement of the correction lens. This may result in anincrease in the size of the entire projection lens.

SUMMARY OF THE INVENTION

The present invention is directed to providing a projection lens inwhich an amount of field curvature is adjustable and which has a smallersize than conventional projection lenses, and a projection displayapparatus using the projection lens.

According to an aspect of the present invention, a projection lensincludes a plurality of lens units, and a diaphragm, wherein theplurality of lens units are configured in such a manner that intervalsbetween adjacent lens units change during zooming or focusing, whereinin a case where a lens unit that moves in an optical axis direction ofthe projection lens during the focusing serves as a focus lens unitamong the plurality of lens units, at least one lens included in a lensunit that is different from the focus lens unit among the plurality oflens units and is disposed more towards a reduction conjugate side thanthe diaphragm is configured to move in the optical axis direction whenan amount of field curvature is adjusted to focus on a curved projectionsurface, and wherein when the amount of field curvature is adjusted,both the at least one lens and the focus lens unit move in the opticalaxis direction.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating a projection lensaccording to a first exemplary embodiment.

FIG. 2 is a diagram illustrating a state in which an image is projectedon a concave curved screen using the projection lens according to thefirst exemplary embodiment.

FIG. 3 is an enlarged view illustrating a state in which an image isprojected on the concave curved screen using the projection lensaccording to the first exemplary embodiment.

FIG. 4 is a diagram illustrating astigmatism in a case where an image isprojected on the concave curved screen using the projection lensaccording to the first exemplary embodiment.

FIG. 5 is a diagram illustrating a state where an image is projected ona convex curved screen using the projection lens according to the firstexemplary embodiment.

FIG. 6 is a diagram illustrating astigmatism in a case where an image isprojected on the convex curved screen using the projection lensaccording to the first exemplary embodiment.

FIG. 7 is a cross-sectional view illustrating a projection lensaccording to a second exemplary embodiment.

FIG. 8 is a diagram illustrating a state where an image is projected onthe concave curved screen using the projection lens according to thesecond exemplary embodiment.

FIG. 9 is an enlarged view illustrating a state in which an image isprojected on the concave curved screen using the projection lensaccording to the second exemplary embodiment.

FIG. 10 is a diagram illustrating astigmatism in a case where an imageis projected on the concave curved screen using the projection lensaccording to the second exemplary embodiment.

FIG. 11 is a diagram illustrating a state where an image is projected onthe convex curved screen using the projection lens according to thesecond exemplary embodiment.

FIG. 12 is a diagram illustrating astigmatism in a case where an imageis projected on the convex curved screen using the projection lensaccording to the second exemplary embodiment.

FIG. 13 is a diagram illustrating a configuration of a projectiondisplay apparatus on which the projection lens according to eachexemplary embodiment is amounted.

FIGS. 14A and 14B are diagrams illustrating graphical user interfaces(GUIs) for adjusting the field curvature.

DESCRIPTION OF THE EMBODIMENTS

Exemplary embodiments of the present invention will be described below.

(Configuration of Projection Display Apparatus)

A projector 100 (projection display apparatus) on which a projectionlens 300 as an image forming optical system according to a first or asecond exemplary embodiment is mounted will be described below withreference to FIG. 13. As illustrated in FIG. 13, the projector 100includes a light source unit (LSU), an illumination optical system(IOS), a color separation system (CSS), and a color combination system200. The projector 100 further includes a red light modulation elementR, a green light modulation element G, a blue light modulation elementB, and the projection lens 300. The projection lens 300 is provided withan operation unit 13 for moving a focus lens unit and a zoom lens unit(described below) in the optical axis direction of the projection lens300.

The LSU, more specifically a high-voltage mercury lamp, can emit whitelight. The LSU may include laser diodes for emitting red light, greenlight, and blue light. The LSU may also include a laser diode foremitting blue light and a phosphor for emitting yellow light.

The white light from the LSU enters the IOS. The IOS includes anintegrator optical system, a polarization conversion element, and acondenser lens unit. The integrator optical system refers to a rodintegrator or two fly-eye lens arrays. The polarization conversionelement can adjust the polarization direction of the white light fromthe LSU to a predetermined polarization direction. The condenser lensunit refers to one positive lens or a set of a plurality of lenseshaving positive power as a whole.

The light from the LSU is formed into light with a uniform illuminationdistribution by the IOS and then divided into red light, green light,and blue light by the CSS. Different color rays of light divided by theCSS enter the three light modulation elements for respective color raysof light. According to the present exemplary embodiment, while all ofthe red light modulation element R, the green light modulation elementG, and the blue light modulation element B are transmissive liquidcrystal panels, these elements may be reflective liquid crystal panelsor micro mirror arrays.

Different color rays of light from the light modulation elements forrespective color rays of light are combined by the color combinationsystem 200 and then led to a screen 600 via the projection lens 300.

A housing for storing the above-described components is provided with aholding unit 400 that can hold the projection lens 300. The projectionlens 300 may or may not be detachable from the holding unit 400.

The IOS, the CSS, and the color combination system 200 are collectivelyconsidered as a light guide optical system for guiding the light fromthe LSU to the light modulation elements and guiding the light from thelight modulation elements to the projection lens 300.

The projection lens 300 according to the first exemplary embodiment willbe described below with reference to FIGS. 1 to 6.

(Overall Configuration of Projection Lens)

FIG. 1 illustrates a lens configuration of a projection lens accordingto the present exemplary embodiment. Referring to FIG. 1 and FIG. 7(described below), the left-hand side of paper is the enlargementconjugate side, and the right-hand side of paper is the reductionconjugate side.

In the projection lens according to the present exemplary embodimentwhich is a fixed focal length projection lens not performing zooming, asecond lens unit L2 and a third lens unit L3 illustrated in FIG. 1 movein the optical axis direction of the projection lens in focusing. Morespecifically, in focusing from infinity to a close distance, theprojection lens performs floating focusing in which the second lens unitL2 and the third lens unit L3 move toward the reduction and theenlargement conjugate sides, respectively, in the optical axis directionof the projection lens along loci different from each other. Thisfloating focusing enables preferably correcting the field curvaturecaused by a change in a projection distance.

A first lens unit L1 and a fourth lens unit L4 do not move for focusing.As described above, the second lens unit L2 and the third lens unit L3are focus lens units which move in the optical axis direction infocusing.

As described above, the projection lens according to the presentexemplary embodiment includes the first lens unit L1 to the fourth lensunit L4 as a plurality of lens units configured in such a manner thatthe intervals between adjacent lens units change in focusing. The changein intervals between adjacent lens units does not only mean that both ofadjacent lens units move in the optical axis direction. Since theintervals between adjacent lens units need only to be changed, theabove-described expression includes a configuration in which either oneof the lens units does not move and the other is movable, like the firstlens unit L1 and the second lens unit L2. Boundaries between a pluralityof lens units can be defined as the intervals between the lenses whichchange in focusing.

A lens unit includes one lens, one pair lens, and a set of a pluralityof lenses. A pair lens refers to a cemented lens, i.e., a pair of twolenses in marginal contact with each other.

(Configuration of Each Lens Unit)

The first lens unit L1 includes eight lenses. In the projection lensaccording to the present exemplary embodiment, the lens disposed on themost enlargement conjugate side is a spherical lens, and the second lensfrom the most enlargement conjugate side is an aspherical lens. The lensdisposed on the most enlargement conjugate side has a large outerdiameter. Forming an aspherical lens having a large outer diameterincreases manufacturing difficulty and manufacturing cost.

According to the present exemplary embodiment, by using an asphericallens as the second lens from the most enlargement conjugate side, themanufacturing difficulty and manufacturing cost are reduced while thefield curvature and distortion are corrected. The third and the fourthlenses from the enlargement conjugate side form a cemented lens. Thefifth, the sixth, and the seventh lenses from the enlargement conjugateside form a cemented lens. This configuration preferably corrects theaxial chromatic aberration.

The second lens unit L2 includes three lenses. The second and thirdlenses from the enlargement conjugate side are aspherical lenses. Thisconfiguration preferably corrects the field curvature. The projectionlens according to the present exemplary embodiment is configured in sucha manner the intermediate image forming point is positioned between thefirst and the second lenses of the second lens unit L2. Thisconfiguration achieves both a wide viewing angle and a small front lensdiameter.

The third lens unit L3 includes one lens.

The fourth lens unit L4 includes eight lenses. The axial chromaticaberration is preferably corrected by forming a cemented lens with thefirst and the second lenses, a cemented lens with the third and thefourth lenses, and a cemented lens with the fifth and the sixth lenses,from the enlargement conjugate side. The fourth lens unit include adiaphragm SP and a field curvature adjustment lens unit FC disposed onthe reduction conjugate side with respect to the diaphragm SP. A memberGB illustrated in FIG. 1 and FIG. 7 (described below) includes, forexample, a prism disposed between the light modulation elements and theprojection lens.

(Configuration for Adjusting Amount of Field Curvature)

A description will be given of a configuration in which a negative lensdisposed on the most enlargement conjugate side is moved in the opticalaxis direction, as a configuration for adjusting the amount of fieldcurvature. The configuration is different from the present exemplaryembodiment. In a projection lens having a wide viewing angle (wide-anglelens), a negative lens having a high refracting power is disposed on themost enlargement conjugate side or at a position near the enlargementconjugate side. Disposing a negative lens on the most enlargementconjugate side makes it easier to achieve both a wide viewing angle anda small front lens diameter than in a case where a positive lens isdisposed on the most enlargement conjugate side.

When the position of a negative lens disposed on the most enlargementconjugate side changes in the optical axis direction, the positionthrough which an off-axis ray passes changes on the lens surface of thenegative lens, and accordingly the amount of field curvature alsochanges. More specifically, by moving the negative lens disposed on themost enlargement conjugate side or a negative lens near the enlargementconjugate side in the optical axis direction, the amount of fieldcurvature can be adjusted, whereby an image with less blur can beprojected on a curved screen.

An off-axis ray passing through the negative lens disposed on the mostenlargement conjugate side has a large angle and a large ray lightheight with respect to the optical axis, and therefore provides a largeeffect of correcting the field curvature by using the negative lens. Inother words, it is possible to reduce the amount of movement of thenegative lens for adjusting the field curvature by a predeterminedamount in the optical axis direction.

However, the increase in viewing angle increases the negative power ofthe negative lens on the most enlargement conjugate side or a negativelens near the enlargement conjugate side. With the increase in thenegative power, the amount of occurrence of the high order aberration ofthe field curvature increases, and the nonlinear characteristics of theamount of occurrence of the field curvature with respect to the imageheight become more remarkable when the negative lens is moved in theoptical axis direction. As a result, the amount of occurrence of thefield curvature of light with a large image height excessivelyincreases, making it difficult to adjust the amount of field curvatureby moving the negative lens disposed on the most enlargement conjugateside in the optical axis direction. More specifically, it becomesdifficult to project an image with less blur on a curved screen.

Further, since both the amount of occurrence of the field curvature andthe astigmatism excessively increase, it becomes difficult to focus onthe entire curved screen. In addition, since the increase in viewingangle increases the diameter of the negative lens disposed on the mostenlargement conjugate side, the size of the entire image forming opticalsystem is increased.

With the projection lens according to the present exemplary embodimentand the second exemplary embodiment (described below), the amount offield curvature is adjusted by moving a lens different from the negativelens disposed on the most enlargement conjugate side in the optical axisdirection. More specifically, with the projection lens according to thepresent exemplary embodiment and the second exemplary embodiment(described below), the amount of field curvature is adjusted by movingthe positive lens disposed on the most reduction conjugate side in theoptical axis direction to change the back focus.

One of reasons why the above-described configuration of the projectionlens according to the present exemplary embodiment and the secondexemplary embodiment (described below) is employed is that the amount offield curvature changes when the back focus changes.

As a feature of a wide-angle lens, there is a tendency that a largeamount of field curvature occurs when the back focus is shifted from thedesign value by the influence of a manufacture error. If an image isprojected on a flat screen with the back focus shifted from the designvalue, a shift occurs between the position of an image display element(light modulation element) and the image forming position of the lens.In other words, the field curvature occurs when the back focus changes.As a result, even if each focus lens unit focuses an image on the centerof the screen, the peripheral portion becomes out of focus. According tothe present exemplary embodiment and the second exemplary embodiment(described below), the field curvature adjustment is performed bychanging the back focus of the projection lens by using this feature.This makes it possible, when an image is projected on a curved screen,to project an image which is in-focus on the entire screen.

A description will be given of the reason why the amount of fieldcurvature changes when the back focus changes. When the back focuschanges, the position where the light from the light modulation elemententers the lens surface of the positive lens disposed on the mostreduction conjugate side changes. According to the present exemplaryembodiment, the position of the image display element with respect tothe projection lens in the optical axis direction is fixed. If theincident position on the lens surface of the positive lens disposed onthe most reduction conjugate side changes, the incident position on thelens surface of the lens more towards the enlargement conjugate sidethan the positive lens also changes. Consequently, the incident positionon the lens surface of the negative lens disposed on the mostenlargement conjugate side changes.

Before the back focus changes, the outmost off-axis ray has been enteredthe position X where the field curvature of the amount A is generated onthe lens surface of the negative lens disposed on the most enlargementconjugate side. In this case, when the back focus changes, the outmostoff-axis ray does not enter the position X but enters the position Ywhere the field curvature of the amount B is generated. Morespecifically, as described above, the amount of field curvature can beadjusted by adjusting the back focus.

(Reason why Image Forming Optical System Smaller than ConventionalSystems can be Achieved)

The amount of field curvature can also be adjusted by changing the backfocus in such a manner that a lens other than the positive lens disposedon the most reduction conjugate side is moved in the optical axisdirection.

A description will be given of a configuration in which the amount offield curvature can be adjusted by adjusting the back focus in such amanner that a lens with high sensitivity to the back focus is moved inthe optical axis direction. With this configuration, the back focus canbe changed by a desired amount by moving the lens a small amount in theoptical axis direction and the amount of field curvature can also beadjusted by a desired. This configuration enables achieving an imageforming optical system which is capable of adjusting the amount of fieldcurvature and is smaller than conventional systems.

Generally, among the lenses disposed on the reduction conjugate sidewith respect to the diaphragm, the lens disposed on the most reductionconjugate side tends to reveal the highest sensitivity to the backfocus. Thus, to achieve a small projection lens, it is desirable toadjust the amount of field curvature by moving the lens disposed on themost reduction conjugate side in the optical axis direction.Alternatively, the amount of field curvature may be adjusted by moving adifferent lens in the optical axis direction.

More specifically, the lens unit disposed at the most reductionconjugate side from among the plurality of lens units (the first lensunit L1 to the fourth lens unit L4) is referred to as the final lensunit, and according to the present exemplary embodiment, the fourth lensunit L4 corresponds to the final lens unit. The field curvatureadjustment lens unit FC as at least one lens included in the final lensunit and disposed on the reduction conjugate side with respect to thediaphragm needs to move in the optical axis direction when the amount offield curvature is adjusted.

According to the present exemplary embodiment, while the field curvatureadjustment lens unit FC is a positive lens disposed on the mostreduction conjugate side, the configuration of the field curvatureadjustment lens unit FC is not limited thereto. Alternatively, forexample, the positive lens disposed on the reduction conjugate side andthe lens adjacent to the positive lens may be integrally moved in theoptical axis direction to adjust the amount of field curvature. Theamount of field curvature may be adjusted by moving, in the optical axisdirection, only the lens adjacent to the positive lens disposed on themost reduction conjugate side. More specifically, the field curvatureadjustment lens unit FC may include at least either one of the lensdisposed on the most reduction conjugate side and the lens adjacent tothis lens.

The field curvature adjustment lens unit FC needs to be at least onelens described below. More specifically, the field curvature adjustmentlens unit FC is at least one of a plurality of lenses that is includedin a lens unit different from the focus lens units, from among theplurality of lens units included in the image forming optical system,and is disposed on the reduction conjugate side with respect to thediaphragm. At least the one lens needs to move in the optical axisdirection of the image forming optical system during field curvatureadjustment. More specifically, the field curvature adjustment lens unitFC may be a lens equivalent to the at least one of a plurality of lensesincluded in a lens unit other than the final lens unit. According toeach exemplary embodiment, the field curvature adjustment lens unit FCmay be replaced with the at least one lens. The field curvatureadjustment lens unit FC may be referred to as a field curvatureadjustment unit FC.

The closer the field curvature adjustment lens unit FC is to thereduction conjugate side, the larger the number of lenses having aneffect of magnifying the field curvature which occurs when the fieldcurvature adjustment lens unit FC moves in the optical axis direction.The larger the number of lenses having this magnifying effect, the lessthe amount of field curvature which occurs in the field curvatureadjustment lens unit FC, and the less the amount of movement of thefield curvature adjustment lens unit FC in the optical axis direction.As a result, the size of the entire image forming optical system can bereduced. Thus, as described above, it is desirable that the fieldcurvature adjustment lens unit FC includes at least either one of thelens disposed on the most reduction conjugate side and the lens adjacentto this lens.

(More Desirable Configuration)

A more desirable configuration according to the present exemplaryembodiment and the second exemplary embodiment will be described below.

According to the present exemplary embodiment, moving the fieldcurvature adjustment lens unit FC in the optical axis direction shiftsthe focus near the optical axis. The field curvature adjustment lensunit FC and the focus lens units are thus simultaneously moved duringfield curvature adjustment. As described above, according to the presentexemplary embodiment, the second lens unit L2 and the third lens unit L3are focus lens units. With this configuration, the amount of fieldcurvature can be adjusted while focus variation near the optical axis isreduced.

In field curvature adjustment, the field curvature adjustment lens unitFC and the focus lens units may be alternately moved in the optical axisdirection instead of being simultaneously moved. In this case, it isdesirable to alternately move the lens units by a minute amount. Withsuch a configuration, the amount of focus variation near the opticalaxis which occurs when the field curvature adjustment lens unit FC andthe focus lens units move in the optical axis direction becomes smallenough with respect to the depth of field of the projection lens. Bymoving these lens units in this way, the amount of field curvature canbe adjusted while focus variation near the optical axis is reduced tosuch an extent that the focus change is negligible within the viewrange.

It is desirable that the projection lens satisfies the followingconditional formula (1):

4.0≤fc/f≤10.0  (1)

when the field curvature adjustment lens unit FC has a focal length fcand the entire projection lens system has a focal length f.

Although the projection lens according to the present exemplaryembodiment is a fixed focal length lens, the projection lens accordingto the second exemplary embodiment (described below) is a zoom lens. Ina case where the projection lens is a zoom lens, the focal length f ofthe entire projection lens system in the conditional formula (1) isreplaced with a focal length fw of the entire projection lens system atthe wide-angle end.

The conditional formula (1) defines the focal length of the fieldcurvature adjustment lens unit FC. If the focal length of the fieldcurvature adjustment lens unit FC is too short and exceeds the lowerlimit of the conditional formula (1), i.e., if the power of the fieldcurvature adjustment lens unit FC is too high, focus variation near theoptical axis excessively increases during field curvature adjustment. Asa result, the amount of movement of the focus lens units for focuscorrection excessively increases. This causes the total lens length ofthe projection lens to extend, which is not desirable. Further, thesensitivity of the field curvature adjustment excessively increases.This degrades the adjustment accuracy, which is not desirable.

If the focal length of the field curvature adjustment lens unit FCexcessively increases and exceeds the upper limit of the conditionalformula (1), i.e., if the power of the field curvature adjustment lensunit FC is too low, the amount of movement for the field curvatureadjustment increases. This causes the total lens length of theprojection lens to be extended, which is not desirable.

It is more desirable that the projection lens satisfies the followingconditional formula (1a):

4.5≤fc/f≤9.6.  (1a)

When the field curvature adjustment lens unit FC has a focal length fcand the focus lens units have a focal length ff, it is desirable thatthe projection lens satisfies the following conditional formula (2):

1.0≤|ff/fc|≤12.0.  (2)

When two or more lens units are focus lens units as in the presentexemplary embodiment, the focal length ff of the focus lens unitsrepresented by the conditional formula (2) is used as a combined focallength of the plurality of lens units. According to the presentexemplary embodiment and the second exemplary embodiment (describedbelow), the focal length ff of the focus lens units indicates the focallength when focusing is performed in a state where a 70-inch projectionimage is projected on the screen. More specifically, according to thepresent exemplary embodiment, the focal length ff indicates the focallength of the focus lens units when focusing is performed in a statewhere a screen and a projector are arranged in such a manner that theprojection image is at 70 inches in size. According to the secondexemplary embodiment (described below), the focal length ff indicatesthe focal length of the focus lens units when focusing is performed in astate where wide-angle end zooming is set, and a screen and a projectorare disposed in such a manner that the projection image is at 70 inchesin size.

The conditional formula (2) defines the balance between the focal lengthof the field curvature adjustment lens unit FC and the focal length ofthe focus lens units. If the focal length ff of the focus lens units istoo short and exceeds the lower limit of the conditional formula (2),i.e., if the power of the focus lens unit is too high, the sensitivityof regular focusing excessively increases. As a result, the accuracy ofregular focusing will be degraded, which is not desirable. Further, thesensitivity of out-of-focus correction near the optical axis duringfield curvature adjustment also excessively increases. This degrades theaccuracy of the out-of-focus correction, which is not desirable. If thefocal length of the field curvature adjustment lens unit FC is too longand exceeds the lower limit of the conditional formula (2), i.e., if thepower of the field curvature adjustment lens unit FC is too low, theamount of movement for the field curvature adjustment increases, asdescribed above.

If the focal length ff of the focus lens unit is too long and exceedsthe upper limit of the conditional formula (2), i.e., if the power ofthe focus lens unit is too low, the amount of movement of the focus lensunits during regular focusing increases. As a result, the total lenslength of the projection lens is extended, which is not desirable.Further, the amount of movement of the focus lens units when anout-of-focus state near the optical axis is corrected during fieldcurvature adjustment also increases. As a result, the total lens lengthof the projection lens is extended, which is not desirable. If the focallength of the field curvature adjustment lens unit FC is too short andexceeds the upper limit of the conditional formula (2), i.e., if thepower of the field curvature adjustment lens unit FC is too high, focusvariation near the optical axis excessively increases during fieldcurvature adjustment, as described above.

It is more desirable that the projection lens satisfies the followingconditional formula (2a):

1.3≤|ff/fc|≤10.0.  (2a)

It is desirable that the field curvature adjustment lens unit FC is onelens or one pair lens. Configuring the field curvature adjustment lensunit FC in this way enables simplifying the structure of a lens barrelfor moving the field curvature adjustment lens unit FC in the opticalaxis direction and saving the weight of the lens barrel. As a result, itbecomes possible to use a small-sized motor having a small driving forceas a motor for moving the field curvature adjustment lens unit FC in theoptical axis direction. This enables reducing the size of mechanicalstructures around the projection lens, thus reducing the size of theentire projector. The above-described pair lens refers to a cementedlens composed of a plurality of lenses and to a plurality of lenses inmarginal contact with each other. It is desirable that the fieldcurvature adjustment lens unit FC is one lens or one pair lens disposedon the most reduction conjugate side from among the plurality of lensesincluded in the projection lens. This configuration enables reducing thesize of the projection lens, as described above.

According to the present exemplary embodiment and the second exemplaryembodiment (described below), it is desirable that the field curvatureadjustment lens unit FC has positive power. Configuring the fieldcurvature adjustment lens unit FC in this way enables reducing the sizeof the final lens unit.

The projection lens according to the present exemplary embodiment is anintermediate image forming (re-image forming) projection lens. Morespecifically, the projection lens according to the present exemplaryembodiment is configured in such a manner that the enlargement conjugatesurface and the intermediate image forming surface disposed inside theprojection lens are conjugated, and the intermediate image formingsurface and the reduction conjugate surface are conjugated.

In a projection lens for a projector using a reflective liquid crystalpanel or a micro mirror array as an image display element, a long backfocus is required to dispose a prism between the projection lens and theimage display element. In a projection lens of non-intermediate imageforming type, achieving both a long back focus and a wide viewing anglerequires a large diameter of the lens on the most enlargement conjugateside (a large front lens diameter). However, in a projection lens ofintermediate image forming type including an optical system with a shortback focus to the intermediate image forming point and a relay opticalsystem with a long back focus from the intermediate image forming pointto the secondary image forming point, both a small front lens diameterand a wide viewing angle can be achieved.

In the projection lens according to the present exemplary embodiment, asillustrated in FIG. 3, an intermediate image forming surface IM ispositioned in the second lens unit L2, and the field curvatureadjustment lens unit FC is disposed on the reduction conjugate side withrespect to the intermediate image forming surface IM. Although, in FIG.3, the intermediate image forming surface IM is drawn by a straight linefor the convenience, the intermediate image forming surface IM isactually distorted. FIG. 3 is an enlarged view illustrating light ofeach angle of field and the projection lens illustrated in FIG. 2 in acase where an image is projected on a curved screen concave toward theprojection lens side, having a curvature radius of 3 m, by using theprojection lens according to the present exemplary embodiment, andfocusing and field curvature adjustment are performed.

Referring to FIGS. 1 and 7, the lower side of paper is the enlargementconjugate side, and the upper side of paper is the reduction conjugateside. Referring to FIGS. 2 and 5, the right-hand side of paper is theenlargement conjugate side, and the left-hand side of paper is thereduction conjugate side. Referring to FIGS. 3 and 9, the upper side ofpaper is the enlargement conjugate side, and the lower side of paper isthe reduction conjugate side.

First Numerical Embodiment

The lens data according to the first numerical embodiment correspondingto the projection lens according to the present exemplary embodimentdescribed above will be presented.

In each numerical embodiment, i denotes the order of optical surfacesfrom the object side, ri denotes the curvature radius of the i-thoptical surface (i-th surface), di denotes the interval between the i-thand the (i+1)-th surfaces, ndi and νdi denote the refractive index andthe Abbe number of the material of the i-th optical member in the dline, respectively. The back focus (BF) indicates the distance from thefinal lens surface to the paraxial image plane and is represented by theair conversion length. An asterisk (*) means an aspherical surface.

The Abbe number of optical materials according to the present numericalembodiment and the second numerical embodiment (described below) will bedescribed. The Abbe number νd is given by the following formula (3):

νd=(nd−1)/(nF−nC)  (3)

when the refractive indexes in the F-line (486.1 nm), the d-line (587.6nm), and the C-line (656.3 nm) of Fraunhofer lines are represented bynF, nd, and nC, respectively.

The aspherical shape is represented as follows:

x=(h ² /R)/[1+{1−(1+k)(h/R)²}^(1/2)]+A4h ⁴ +A6h ⁶ +A8h ⁸ +A10h ¹⁰

when k denotes the eccentricity, A4, A6, A8, and A10 denote asphericalcoefficients, and x denotes the displacement in the optical axisdirection at the position with a height h from the optical axis withreference to the surface vertex, where R denotes the paraxial curvatureradius.

(Surface Data Unit mm)

Surface number r d nd νd  1 56.355 4.00 1.67790 55.3  2 31.205 7.10  3*78.564 3.50 1.58313 59.4  4* 13.443 24.20  5 −16.798 1.50 1.84666 23.8 6 71.641 5.00 1.59349 67.0  7 −13.736 0.50  8 66.110 6.50 1.59349 67.0 9 −18.666 1.40 1.84666 23.8 10 71.418 6.50 1.59349 67.0 11 −31.03722.00 12 93.205 8.50 1.80810 22.8 13 −163.973 8.74 14* 36.283 10.001.90366 31.3 15 100.787 52.65 16* 77.693 3.00 1.58313 59.4 17* 14.17816.60 18 −314.339 7.50 1.83481 42.7 19 −35.842 32.30 20 46.341 5.501.48749 70.2 21 −153.281 7.21 22 551.642 1.50 1.48749 70.2 23 27.3604.80 1.80810 22.8 24 69.109 12.90 25(Diaphragm) ∞ 8.00 26 −218.122 1.501.84666 23.8 27 29.287 6.00 1.48749 70.2 28 −27.368 3.50 29 −18.484 1.501.90366 31.3 30 86.677 6.50 1.51633 64.1 31 −28.781 0.50 32 369.801 9.501.43875 94.7 33 −25.255 3.80 34 62.226 5.80 1.77250 49.6 35 ∞ 5.00 36 ∞37.00 1.51633 64.1 37 ∞ 4.00 38 ∞ 19.50 1.80518 25.4 39 ∞ 5.80 Imageplane ∞

(Aspherical Surface Data)

Third surface K = 0.00000e+000 A4 = 2.23482e−005 A6 = −2.84117e−008 A8 =3.84260e−011 A10 = −2.47414e−014 Fourth surface K = −5.84328e−001 A4 =−4.57376e−005 A6 = 1.85652e−007 A8 = −6.68736e−010 A10 = 2.49098e−013Fourteenth surface K = 0.00000e+000 A4 = −2.80744e−006 A6 =−3.10707e−010 A8 = −1.83015e−012 A10 = 1.45035e−015 A12 = −1.30506e−018Sixteenth surface K = 0.00000e+000 A4 = −4.24838e−005 A6 = 7.20396e−008A8 = −1.15539e−010 A10 = 1.40383e−013 Seventeenth surface K =−4.28203e−001 A4 = −8.67428e−005 A6 = 3.23464e−008 A8 = 1.17289e−010 A10= −8.48144e−013

(Various Data)

Focal length 8.51 F number 2.40 Half angle of field 59.16 Image height14.25 Total lens length 349.85 BF 44.85

(Lens Unit Data)

Unit Starting surface Focal length 1 1 25.59 2 14 104.61 3 20 73.44 4 2260.29

FIG. 4 is a diagram illustrating astigmatism in the case of FIGS. 2 and3, and FIG. 6 is a diagram illustrating astigmatism in the case of FIG.5. FIG. 5 is a diagram illustrating light of each angle of field and theprojection lens in a case where an image is projected on a curved screenconvex toward the projection lens side, having a curvature radius of 8m, by using the projection lens according to the present exemplaryembodiment, and focusing and field curvature adjustment are performed.Referring to FIGS. 4 and 6, the solid lines indicate astigmatism oflight with a wavelength of 550 nm on a sagittal image plane, and thedotted lines illustrate astigmatism of light with a wavelength of 550 nmon a meridional image plane. The half angle of field is denoted by ω andω is at 59 degrees in FIGS. 4 and 6. As illustrated in FIGS. 4 and 6,the projection lens according to the present exemplary embodiment canimprove astigmatism in comparison between before and after the fieldcurvature adjustment.

A projection lens (image forming optical system) according to the secondexemplary embodiment will be described below with reference to FIGS. 7to 12.

(Overall Configuration of Projection Lens)

FIG. 7 illustrates a lens configuration of the projection lens accordingto the present exemplary embodiment. The projection lens according tothe present exemplary embodiment is a zoom lens which includes a firstlens unit L1 to a seventh lens unit L7 as a plurality of lens units anda diaphragm SP. The diaphragm SP is disposed more towards theenlargement conjugate side than the seventh lens unit L7. Morespecifically, the diaphragm SP is disposed between the third lens unitL3 and the fourth lens unit L4.

The first lens unit L1 to the seventh lens unit L7 are disposed in sucha manner that intervals between adjacent lens units change in zooming.More specifically, the first lens unit L1 and the seventh lens unit L7do not move in zooming. In zooming from the wide-angle end to thetelephoto end, the second lens unit L2 to the sixth lens unit L6 and thediaphragm SP move to the enlargement conjugate side in the optical axisdirection of the projection lens along loci different from each other.Boundaries between a plurality of lens units can also be defined as theintervals between lenses which change in zooming.

The first lens unit L1 includes a plurality of sub-lens units configuredin such a manner that the intervals between adjacent sub-lens unitschange in focusing. According to the present exemplary embodiment, theplurality of sub-lens units includes the first sub-lens unit SL1, thesecond sub-lens unit SL2, and the third sub-lens unit SL3. In focusing,the second sub-lens unit SL2 and third sub-lens unit SL3 move in theoptical axis direction of the projection lens. More specifically, thefirst sub-lens unit SL1 does not move in focusing. In focusing frominfinity to a close distance, the second sub-lens unit SL2 and the thirdsub-lens unit SL3 move to the reduction conjugate side along locidifferent from each other. With this configuration, variation of thefield curvature in focusing can be reduced. The second lens unit L2 tothe seventh lens unit L7 do not move in focusing.

The seventh lens unit L7 includes the field curvature adjustment lensunit FC.

(Configuration of Each Lens Unit)

The first lens unit L1 includes four lenses and one cemented lens. Morespecifically, the first sub-lens unit SL1 includes three lenses, thesecond sub-lens unit SL2 includes one negative lens, and the thirdsub-lens unit SL3 includes one cemented lens. The first and the secondlenses from the enlargement conjugate side from among the lensesincluded in the first lens unit L1 are aspherical lenses. Theseaspherical lenses are provided with an effect of correcting the fieldcurvature and distortion.

Each of the second lens unit L2 and the third lens unit L3 includes onelens. Each of the fourth lens unit L4 and the fifth lens unit L5includes one cemented lens. With this configuration, the axial chromaticaberration in the entire zoom range can be favorably corrected.

The sixth lens unit L6 includes one cemented lens and one lens. Theseventh lens unit L7 includes one lens.

According to the present exemplary embodiment, the diaphragm SP moves inthe optical axis direction of the projection lens along a locusdifferent from the loci of the lens units in zooming. The aperturediameter of the diaphragm SP is constant in zooming. However, thediaphragm SP may be integrated with the third lens unit L3 or the fourthlens unit L4. Further, by making the aperture diameter of the diaphragmSP variable, ghost and flare by unnecessary light may be eliminated toimprove the contrast of a projection image.

(Configuration for Adjusting Amount of Field Curvature)

According to the present exemplary embodiment, similarly to theabove-described first exemplary embodiment, the final lens unit includesthe field curvature adjustment lens unit FC to adjust the amount offield curvature with a configuration similar to the first exemplaryembodiment. According to the present exemplary embodiment, the finallens unit is the seventh lens unit L7. Therefore, according to thepresent exemplary embodiment, a similar effect obtained by the firstexemplary embodiment can be obtained. A more desirable configuration,for example, a configuration different from the projection lensaccording to the first exemplary embodiment, may be applied to thepresent exemplary embodiment.

Second Numerical Embodiment

The lens data according to the second numerical embodiment correspondingto the above-described projection lens according to the presentexemplary embodiment is as follows.

(Surface Data Unit Mm)

Surface number r d nd νd  1* 330.256 5.00 1.65160 58.5  2 55.262 27.84  3* 84.396 3.00 1.83481 42.7  4 36.392 15.53   5 −58.066 2.00 1.4387594.7  6 49.389 14.43   7 −112.104 2.00 1.77250 49.6  8 554.177 4.00  995.914 2.30 1.92286 20.9 10 59.911 11.71  1.60342 38.0 11 −52.551(Variable) 12 71.750 2.75 1.58913 61.1 13 139.420 (Variable) 14 82.4512.78 1.80518 25.5 15 727.084 (Variable) 16 (Diaphragm) ∞ (Variable) 1797.753 3.33 1.51633 64.1 18 −56.305 1.30 1.90366 31.3 19 −110.664(Variable) 20 −161.174 1.20 1.90366 31.3 21 29.682 4.90 1.51633 64.1 22−53.464 (Variable) 23 −26.413 1.30 1.90366 31.3 24 86.880 4.70 1.5163364.1 25 −40.873 1.00 26 195.670 9.13 1.49700 81.5 27 −31.111 (Variable)28 101.853 4.34 1.80810 22.8 29 −167.363 5.00 30 ∞ 37.00  1.51633 64.131 ∞ 4.00 32 ∞ 19.50  1.80518 25.4 33 ∞ 5.80 Image plane ∞

(Aspherical Surface Data)

First surface K = 0.00000e+000 A4 = 2.45572e−006 A6 = −1.02519e−009 A8 =5.16476e−013 A10 = −1.44875e−016 A12 = 2.07693e−020 Third surface K =0.00000e+000 A4 = −3.54628e−006 A6 = 1.89251e−009 A8 = −2.53514e−012 A10= 2.52440e−015 A12 = −9.46913e−019

(Various Data)

Zoom ratio 1.30 Wide angle Intermediate Telephoto Focal length 13.3115.45 17.29 F number 2.57 2.60 2.60 Half angle of field 45.50 41.2338.07 Image height 13.54 13.54 13.54 Total lens length 298.43 298.41298.40 BF 49.82 49.80 49.79 d11 79.56 60.00 42.94 d13 4.98 11.93 20.62d15 19.11 25.81 32.01 d16 12.89 9.39 3.87 d19 2.50 2.54 4.57 d22 3.013.48 2.20 d27 2.00 10.91 17.84

(Lens Unit Data)

Unit Starting surface Focal length 1 1 −41.93 2 12 246.33 3 14 114.33 417 152.49 5 20 −116.63 6 23 −1336.63 7 28 78.21

(Sub-Lens Unit Data)

Unit Starting surface Focal length 1 1 −18.42 2 7 −120.03 3 9 64.95

FIG. 10 is a diagram illustrating astigmatism in the case of FIGS. 8 and9, and FIG. 12 is a diagram illustrating astigmatism in the case of FIG.11. FIG. 8 illustrates light of each angle of field and the projectionlens in a case where an image is projected on a curved screen concavetoward the projection lens side, having a curvature radius of 3 m, byusing the projection lens according to the present exemplary embodiment,and focusing and field curvature adjustment are performed. FIG. 9 is anenlarged view illustrating the projection lens illustrated in FIG. 8.FIG. 11 is a diagram illustrating light of each angle of field and theprojection lens in a case where an image is projected on a curved screenconvex toward the projection lens side, having a curvature radius of 8m, by using the projection lens according to the present exemplaryembodiment, and focusing and field curvature adjustment are performed.Referring to FIGS. 8 and 11, the focal length of the projection lens isthe focal length at the wide-angle end.

Referring to FIGS. 10 and 12, the solid lines indicate astigmatism oflight with a wavelength of 550 nm on a sagittal image plane, and thedotted lines indicate astigmatism of light with a wavelength of 550 nmon a meridional image plane. The half angle of field is denoted by ω andω is at 45.3 degrees in FIGS. 10 and 12. As illustrated in FIGS. 10 and12, the projection lens according to the present exemplary embodimentcan improve astigmatism in comparison between before and after the fieldcurvature adjustment.

Table 1 illustrates results of calculations by the conditional formulas(1) and (2) according to the first and the second exemplary embodiments.

TABLE 1 First exemplary Second exemplary embodiment embodimentConditional formula (1) fc/f 9.43 5.88 Conditional formula (2) |ff/fc|9.09 1.51 Focal length of entire system (f) 8.51 13.31 Focal length offield curvature 80.21 78.21 adjustment lens unit FC (fc) Focal length offocus lens unit (ff) −728.85 118.13

While the present invention has specifically been described based on theabove-described preferred exemplary embodiments, the present inventionis not limited thereto but can be modified in diverse ways within theambit of the appended claims.

For example, the exemplary embodiments have been described centering ona configuration of a projection lens as an image forming optical system,the configurations of the exemplary embodiments may be applied to animaging optical system for camera as an image forming optical system.

When the amount of field curvature is adjusted, both the field curvatureadjustment lens unit FC and the focus lens units are moved in theoptical axis direction of the image forming optical system. Morespecifically, as described above, when the amount of field curvature isadjusted, the field curvature adjustment lens unit FC and the focus lensunits may simultaneously or alternately move in the optical axisdirection. Further, when the amount of field curvature is adjusted, thefocus lens units may move in the optical axis direction after the fieldcurvature adjustment lens unit FC moves in the optical axis direction.

In the image forming optical system, the above-described exemplaryembodiments focuses on the field curvature adjustment lens unit FCdisposed more towards the reduction conjugate side than the diaphragm.However, the following configuration out of the configurations of theimage forming optical systems according to the first exemplaryembodiment may be focused. More specifically, in an image formingoptical system of intermediate image forming type, the amount of fieldcurvature is adjusted by moving in the optical axis direction at leastone of a plurality of lenses included in a lens unit different from thefocus lens unit.

A description will be given of graphical user interfaces (GUIs)displayed on a screen to enable the user to perform field curvatureadjustment on the projector illustrated in FIG. 13, with reference toFIGS. 14A and 14B. FIG. 14A is a diagram illustrating a GUI displayedwhen regular focusing (a focusing operation for focusing the screencenter) is performed.

The user operates an operation unit, such as a cross key, disposed on aremote control or projector (not illustrated) in the vertical (orhorizontal) direction. Then, an actuator in the projector for moving thefocus lens units in the optical axis direction is driven. As a result,the focus lens units move in association with a cross key operation bythe user, and focusing is performed. In this process, the upper end of aslider bar 500 on paper in the GUI illustrated in FIG. 14A verticallymoves in association with the cross key operation by the user.

The GUI illustrated in FIG. 14B will be described below. When the useroperates the cross key in the vertical (or horizontal) direction, theactuator in the projector for moving the field curvature adjustment lensunit FC in the optical axis direction is driven. As a result, the fieldcurvature adjustment lens unit FC moves in association with a cross keyoperation by the user, and the adjustment of the amount of fieldcurvature is performed. In this case, similarly to the GUI illustratedin FIG. 14A, the upper end of the slider bar 500 on paper in the GUIillustrated in FIG. 14B vertically moves in association with the crosskey operation by the user.

Instead of a cross key disposed on a remote control or projector, anelectronic cross key displayed on the screen of a portable terminal suchas a smart phone may also be used.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

What is claimed is:
 1. A projection lens for projecting an image on a curved projection surface by adjusting an amount of field curvature, comprising: a plurality of lens units; and a diaphragm, wherein the plurality of lens units are configured in such a manner that intervals between adjacent lens units change during zooming or focusing, wherein a focus lens unit among the plurality of lens units is configured to move in an optical axis direction of the projection lens during the focusing, wherein at least one lens included in a lens unit that is different from the focus lens unit among the plurality of lens units is disposed more towards a reduction conjugate side than the diaphragm, and wherein when the amount of field curvature is adjusted, both the at least one lens and the focus lens unit are configured to move in the optical axis direction.
 2. The projection lens according to claim 1, wherein when the amount of field curvature is adjusted, the at least one lens and the focus lens unit are configured to move simultaneously in the optical axis direction.
 3. The projection lens according to claim 1, wherein when the amount of field curvature is adjusted, the focus lens unit moves in the optical axis direction after the at least one lens moves in the optical axis direction.
 4. The projection lens according to claim 1, wherein when the amount of field curvature is adjusted, the at least one lens and the focus lens unit are configured to move alternately in the optical axis direction.
 5. The projection lens according to claim 1, wherein the following formula is satisfied: 4.0≤fc/f≤10.0 when the at least one lens has a focal length fc and the projection lens has a focal length f.
 6. The projection lens according to claim 5, wherein the following formula is satisfied: 4.5≤fc/f≤9.6.
 7. The projection lens according to claim 1, wherein the following formula is satisfied: 1.0≤|ff/fc|≤12.0 when the at least one lens has a focal length fc and the focus lens unit has a focal length ff.
 8. The projection lens according to claim 7, wherein the following formula is satisfied: 1.3≤|ff/fc|≤10.0.
 9. The projection lens according to claim 1, wherein the plurality of lens units includes: a first lens unit; a second lens unit; a third lens unit; and a fourth lens unit, arranged from an enlargement conjugate side to the reduction conjugate side, wherein the first, the second, the third, and the fourth lens units are configured in such a manner that that intervals between adjacent lens units change during focusing, wherein the first and the fourth lens units do not move during focusing, wherein the second and the third lens units are the focus lens units that move in the optical axis direction during focusing, and wherein the diaphragm and the at least one lens are included in the fourth lens unit.
 10. The projection lens according to claim 9, wherein when focusing is performed from infinity to a close distance, the second lens unit moves to the reduction conjugate side, and the third lens unit moves to the enlargement conjugate side.
 11. The projection lens according claim 1, wherein the plurality of lens units includes: a first lens unit; a second lens unit; a third lens unit; a fourth lens unit; a fifth lens unit; a sixth lens unit; and a seventh lens unit, arranged from an enlargement conjugate side to the reduction conjugate side, wherein the first, the second, the third, the fourth, the fifth, the sixth, and the seventh lens units are configured in such a manner that intervals between adjacent lens units change during zooming, wherein the first and the seventh lens units do not move during zooming, wherein the second, the third, the fourth, the fifth, and the sixth lens units move in the optical axis direction during zooming, and wherein the at least one lens is included in the seventh lens unit.
 12. The projection lens according to claim 11, wherein the diaphragm is disposed more towards the enlargement conjugate side than the seventh lens unit.
 13. The projection lens according to claim 11, wherein, in zooming from a wide-angle end to a telephoto end, the second, the third, the fourth, the fifth, and the sixth lens units are configured to move to the enlargement conjugate side.
 14. The projection lens according to claim 11, wherein the first lens unit includes a first sub-lens unit, a second sub-lens unit, and a third sub-lens unit which are configured in such a manner that intervals between adjacent sub-lens units change during focusing, and wherein the second and the third sub-lens units are the focus lens units that move in the optical axis direction during focusing.
 15. The projection lens according to claim 14, wherein the first sub-lens unit is configured not to move during focusing, and wherein during focusing from infinity to a close distance, the second and the third sub-lens units are configured to move to the reduction conjugate side.
 16. The projection lens according to claim 1, wherein the at least one lens is one lens or one pair of lenses.
 17. The projection lens according to claim 16, wherein the at least one lens has positive power.
 18. The projection lens according to claim 1, wherein the projection lens is configured in such a manner that an enlargement conjugate surface and an intermediate image forming surface disposed inside the projection lens are conjugated, and the intermediate image forming surface and a reduction conjugate surface are conjugated.
 19. A projection lens for projecting an image on a curved projection surface by adjusting an amount of field curvature, comprising: a plurality of lens units, wherein the plurality of lens units are configured in such a manner that intervals between adjacent lens units change during zooming or focusing, wherein the projection lens is configured in such a manner that an enlargement conjugate surface and an intermediate image forming surface disposed inside the projection lens are conjugated, and the intermediate image forming surface and a reduction conjugate surface are conjugated, and wherein in a case where a lens unit that moves in an optical axis direction of the projection lens during the focusing serves as a focus lens unit among the plurality of lens units, at least one lens included in a lens unit different from the focus lens unit, among the plurality of lens units, is configured to move in the optical axis direction when the amount of field curvature is adjusted.
 20. A projection lens for projecting an image on a curved projection surface by adjusting an amount of field curvature, comprising: a plurality of lens units; and a diaphragm, wherein the plurality of lens units are configured in such a manner that intervals between adjacent lens units change during zooming or focusing, wherein a focus lens unit among the plurality of lens units is configured to move in an optical axis direction of the projection lens during the focusing, wherein at least one lens included in a lens unit that is different from the focus lens unit, among the plurality of lens units, is disposed more towards a reduction conjugate side than the diaphragm, wherein the at least one lens is configured to move in the optical axis direction when the amount of field curvature is adjusted, and wherein the following formula is satisfied: 4.0≤fc/f≤10.0 when the at least one lens has a focal length fc and the projection lens has a focal length f.
 21. A projection lens for projecting an image on a curved projection surface by adjusting an amount of field curvature, comprising: a plurality of lens units; and a diaphragm, wherein the plurality of lens units are configured in such a manner that intervals between adjacent lens units change during zooming or focusing, wherein a focus lens unit among the plurality of lens units is configured to move in an optical axis direction of the projection lens during the focusing, wherein at least one lens included in a lens unit that is different from the focus lens unit, among the plurality of lens units, is disposed more towards a reduction conjugate side than the diaphragm, wherein the at least one lens is configured to move in the optical axis direction when the amount of field curvature is adjusted, and wherein the following formula is satisfied: 1.0≤|ff/fc|≤12.0 when the at least one lens has a focal length fc and the focus lens unit has a focal length ff.
 22. The projection lens according to claim 1, wherein the at least one lens is configured not to move during focusing.
 23. The projection lens according to claim 1, wherein the at least one lens is configured not to move during zooming.
 24. A projection display apparatus comprising: a light source; a light modulation element; a projection lens; and a light guide optical system configured to guide light from the light source to the light modulation element and guide the light from the light modulation element to the projection lens, wherein the projection lens that projects an image on a curved projection surface by adjusting an amount of field curvature, includes: a plurality of lens units; and a diaphragm, wherein the plurality of lens units are configured in such a manner that intervals between adjacent lens units change during zooming or focusing, wherein a focus lens unit among the plurality of lens unit is configured to move in an optical axis direction of the projection lens during the focusing, wherein at least one lens included in a lens unit that is different from the focus lens unit among the plurality of lens units is disposed more towards a reduction conjugate side than the diaphragm, and wherein when the amount of field curvature is adjusted, both the at least one lens and the focus lens unit are configured to move in the optical axis direction.
 25. A projection display apparatus comprising: a light source; a light modulation element; a projection lens; and a light guide optical system configured to guide light from the light source to the light modulation element and to guide the light from the light modulation element to the projection lens, wherein the projection lens that projects an image on a curved projection surface by adjusting an amount of field curvature, includes: a plurality of lens units, wherein the plurality of lens units are configured in such a manner that intervals between adjacent lens units change during zooming or focusing, wherein the projection lens is configured in such a manner that an enlargement conjugate surface and an intermediate image forming surface disposed inside the projection lens are conjugated, and the intermediate image forming surface and a reduction conjugate surface are conjugated, and wherein in a case where a lens unit that moves in an optical axis direction of the projection lens during focusing serves as a focus lens unit among the plurality of lens units, at least one lens included in a lens unit that is different from the focus lens unit among the plurality of lens units is configured to move in the optical axis direction when the amount of field curvature is adjusted.
 26. A projection display apparatus comprising: a light source; a light modulation element; a projection lens; and a light guide optical system configured to guide light from the light source to the light modulation element and to guide the light from the light modulation element to the projection lens, wherein the projection lens that projects an image on a curved projection surface by adjusting an amount of field curvature, includes: a plurality of lens units; and a diaphragm, wherein the plurality of lens units are configured in such a manner that intervals between adjacent lens units change during zooming or focusing, wherein a focus lens unit among the plurality of lens units is configured to move in an optical axis direction of the projection lens during the focusing, wherein at least one lens included in a lens unit that is different from the focus lens unit among the plurality of lens units is disposed more towards a reduction conjugate side than the diaphragm, wherein the at least one lens is configured to move in the optical axis direction when the amount of field curvature is adjusted, and wherein the following formula is satisfied: 4.0≤fc/f≤10.0 when the at least one lens has a focal length fc and the projection lens has a focal length f.
 27. A projection display apparatus comprising: a light source; a light modulation element; a projection lens; and a light guide optical system configured to guide light from the light source to the light modulation element and to guide the light from the light modulation element to the projection lens, wherein the projection lens that projects an image on a curved projection surface by adjusting an amount of field curvature, includes: a plurality of lens units; and a diaphragm, wherein the plurality of lens units are configured in such a manner that intervals between adjacent lens units change during zooming or focusing, wherein a focus lens unit among the plurality of lens units is configured to move in an optical axis direction of the projection lens during the focusing, wherein at least one lens included in a lens unit that is different from the focus lens unit among the plurality of lens units is disposed more towards a reduction conjugate side than the diaphragm, wherein the at least one lens is configured to move in the optical axis direction when the amount of field curvature is adjusted, and wherein the following formula is satisfied: 1.0≤|ff/fc|≤12.0 when the at least one lens has a focal length fc and the focus lens unit has a focal length ff. 